1. Field of the Invention
This invention relates to a friction test apparatus for viscoelastic materials such as rubber, etc. To describe further in detail, this invention relates to a friction test apparatus with which similar effects to that of friction test of prototype tires are obtained by conducting friction test with a sample of composition material of the tire and without making various prototype tires.
2. Description of the Related Art Conventionally, as a friction test apparatus for viscoelastic materials for tires, a friction test apparatus of slide resistance type in which friction test is conducted by sliding a sample composed of a viscoelastic material on a friction face, and a friction test apparatus of rotating disc type as disclosed by Japanese Patent Publication Number 3-10062 are in the mainstream. And, a friction test apparatus of rotation type on the road as disclosed by Japanese Patent Publication Number 3-63012 is also proposed.
Further, as friction test apparatuses of recent types, an apparatus in which a sample is made contact an inner face of a cylindrical rotating drum to conduct friction test, an apparatus of slide resistance type in which friction characteristics on an actual road are measured as disclosed by Japanese Utility Model Provisional Publication Number 5-66545, and an improved type of the cylindrical rotating drum as disclosed by Japanese Patent Provisional Publication Number 6-221990 are also proposed.
However, in these conventional apparatuses as described above, following problems occurs.
{circle around (1)} In friction test apparatuses of slide resistance type, slide resistance is mainly measured because the resistance is measured with the sample sliding on the friction face. Although rolling resistance should be measured in friction test of a tire, friction data of the friction test with slide resistance are used, and the test condition is different from actual service condition.
{circle around (2)} In the apparatuses in which the sample is made contact and rotated on the inner face or the outer face of the rotating drum, curved faces of the rotating drum and the sample contact each other, load distribution on the sample is different from that in actual service conditions of a tire when the load is increased, and reliability of the test becomes low thereby.
{circle around (3)} In the apparatus in which the sample is made contact and rotated on a rotating flat board to conduct friction test, centrifugal force always works on the sample outward, and difference of rotation speed on an inner side and an outer side of the flat board generates difference in rotation speed against the flat board on an inner part and an outer part of the sample. Measured value of the friction considerably varies depending on interpretation of the difference in the rotation speed.
{circle around (4)} To solve the problems of {circle around (2)} and {circle around (3)}, it is feasible to make the rotation body (the rotating drum or the flat board) larger than the sample. Although the measurement is improved to some degrees with this modification, it is insufficient to obtain accurate test results. And, this modification causes a problem that the apparatus itself becomes large.
It is therefore an object of the present invention, solving the problems above, to provide a friction test apparatus in which friction test of a viscoelastic material is easily and accurately conducted by simulating friction test with a sample of product and without making prototypes of actual product.